Bacterial products, cytokines and sleep.

Sleep deprivation, infection and administration of muramyl peptides or certain other immune response modifiers all alter sleep. Sleep, temperature and hematologic effects observed after bacterial infection are also elicited after administration of isolated bacterial cell walls. Macrophages have the capability to digest bacterial peptidoglycan and in the process produce pyrogenic and somnogenic substances of low molecular weight. Activated macrophages also produce cytokines and some of these, e.g., interleukin-1 (IL-1), are somnogenic. Our results emphasize the close connection of the infection process, fever and sleep. Muramyl peptides and/or IL-1 may also be involved in daily regulation of sleep.